A large number of devices have been provided in the prior art, particularly for use by golfers, as a training device or aid to assure that the golfer is properly addressing the ball and maintaining his stance during both the backstroke and forward stroke when hitting the ball with a golf club. Many of these prior art devices have also included a plumb bob or vertical plumb device to provide a true vertical reference for the golfer. A number of these 20 devices are summarized immediately below in order to provide a better understanding of the prior art.
Initially, U.S. Pat. No. 3,109,654 issued Nov. 5, 1963 is representative of a number of U.S. patents relating to devices which can be attached to golfer's caps or other headwear. These devices generally included a plumb bob freely suspended from the cap. Generally, the plumb bob permits the golfer to be aware of any movement in the plumb bob as an indication of whether or not the golfer moves his head while addressing and striking the ball. It is generally understood that such movement of the head is undesirable.
Similar devices including a suspended plumb bob attached to a golfer's cap or the like were provided in U.S. Pat. No. 3,178,187 issued Apr. 13, 1965; U.S. Pat. No. 3,437,339 issued Apr. 8, 1969; and U.S. Pat. No. 3,951,414 issued Apr. 20, 1976. U.S. Pat. No. 4,098,509 issued July 4, 1978 is another related prior art reference which does not include a suspended plumb bob but rather includes a device attached to a golfer's hat for providing an audible signal if the golfer moves his head while addressing or hitting a golf ball.
U.S. Pat. No. 3,826,502 issued July 30, 1974 and U.S. Pat. No. 4,079,940 issued Mar. 21, 1978 both disclosed attachments for golfer's caps including a fixed loop or other means through which the golfer sights the ball while addressing it. Here again, the purpose of these attachments is to assure that the golfer does not move his head while addressing and striking the ball.
Finally, U.S. Pat. No. 3,860,246 issued Jan. 14, 1975 disclosed yet another device with a plumb or pendulum being suspended from the golfer's mouth for the same purpose of preventing movement of the golfer's head.
These prior art devices are generally indicative of the desire for means to assist golfers in improving their skills. However, most of these devices are directed toward the stance or position of the golfer himself. Yet other well-known devices are available for assisting the golfer in assessing distance. Such devices are not discussed in greater detail herein. However, a number of techniques have been employed in the design of devices for this purpose.
Even with this variety of devices available to the golfer, there has been found to remain a need for a device for use by golfers and the like in rapidly assessing inclination of terrain transverse to his sight line. For example, during approach shots on a green or on the green itself, it is often particularly important for the golfer to be able to accurately assess transverse inclination of terrain along the green between his ball and the hole. The utility of such a device for golfers and others is believed obvious.